Selected Quarterly Financial Data (Unaudited) - Schedule of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues, net	$ 609,991	$ 577,877	$ 541,237	$ 520,433	$ 514,953	$ 484,426	$ 417,905	$ 414,262	$ 2,249,538	$ 1,831,546	$ 1,702,865
Operating income:	240,012	232,637	216,043	195,068	215,975	191,055	171,168	175,955	883,760	754,153	667,534
Net income	$ 282,697	$ 202,823	$ 130,987	$ 123,693	$ 95,424	$ 129,618	$ 116,253	$ 111,090	$ 740,200	$ 452,385	$ 362,431
Earnings per share:
Basic earnings per share (in usd per share)	$ 3.15	$ 2.23	$ 1.42	$ 1.34	$ 1.03	$ 1.40	$ 1.25	$ 1.20	$ 8.12	$ 4.89	$ 3.94
Diluted earnings per share (in usd per share)	$ 3.05	$ 2.18	$ 1.39	$ 1.31	$ 1.00	$ 1.36	$ 1.22	$ 1.17	$ 7.91	$ 4.75	$ 3.85
Weighted average shares outstanding:
Basic weighted average shares outstanding (in shares)	89,676	90,751	92,013	92,108	92,574	92,631	92,665	92,516	91,129	92,597	92,023
Diluted weighted average shares outstanding (in shares)	92,623	93,001	94,223	94,560	95,235	95,307	95,279	95,030	93,594	95,213	94,139